Field
The present disclosure relates to the field of transportation aerodynamics. More specifically, disclosed is an apparatus to improve aerodynamic and fuel efficiency of an over-the-road cargo vehicle.
Related Art
The predominant mode of transportation for commercial goods throughout the United States, the developed world and elsewhere is cargo truck, among these including a tractor-trailer truck. For this mode of transportation, fuel represents the largest single cost component. Therefore, any measureable improvement in fuel efficiency of such vehicles is worthwhile.
In particular, in the developed world, where tractor-trailer trucks travel long distances of well-developed highways at a generally high speed, aerodynamic drag represents a major source of inefficiency. One source of such aerodynamic inefficiency is the geometry of the truck, which is essentially an elongated rectangular prism. In particular, the airflow properties over the trailing edge of the trailer create a large trailing negative pressure vortex, which greatly contributes to drag.
One recent technology to improve aerodynamic efficiency is colloquially called a “boat tail”. A boat tail is an attachment to the rear end of the trailer which acts as a fairing to gradually reduce the cross-sectional area of the trailer, and thus reduce the size and intensity of the trailing vortex and its associated drag. One investigation by the Platform for Aerodynamic Road Transport (PART), a research affiliate of the Delft University of Technology, Netherlands, suggests a boat tail can contribute a 4.5% improvement in fuel efficiency.
However, a boat tail as it is currently practiced has a practical size limit that still necessitates an abrupt geometry change at its trailing edge. Furthermore, a trailer is accessed via doors at its rear. Any sort of boat tail impedes access to such doors. For many such tractor/trailer trucks the container itself is transferable in order to be used by intermodal transportation (i.e., train, or cargo ship). In those circumstances, the aerodynamics are either substantially different (e.g. rail), or not even a concern (i.e., container ship). In such cases, the inviolable requirement is that the container keep its standardized size and shape, to enable its intermodal transfer. Permanent alterations to the shape of the trailer to improve efficiency are therefore impossible, to say nothing of the cost-effectiveness in construction of a box trailer. Even an aerodynamically effective successful boat tail should therefore be temporary, removable or interchangeable for most practical effect.
Furthermore, in loading or unloading, a road-use trailer is most commonly backed up to an elevated loading dock. Attempts to deal with this problem include making the boat tail inflatable, or foldable. Still, a boat tail remains an operational obstacle to loading and unloading.
Therefore, the present state of the art is lacking. Other solutions in place of or in addition to a boat tail may yield even better aerodynamic results and/or greater operational advantages.